Loops: For, While, and Do-While

Loops let you repeat a block of code multiple times without rewriting it — essential for processing collections of data, counting, and repeated calculations.

The For Loop

Best when you know exactly how many times to repeat.

for (int i = 1; i <= 5; i++) {
    System.out.println("Count: " + i);
}
// Prints Count: 1 through Count: 5

The three parts: int i = 1 (initialization, runs once), i <= 5 (condition, checked before every iteration), i++ (update, runs after every iteration).

The While Loop

Best when the number of repetitions is not known upfront and depends on a condition.

int count = 0;
while (count < 5) {
    System.out.println("Count: " + count);
    count++;
}

The Do-While Loop

Guarantees the loop body runs at least once, since the condition is checked after the first execution.

int num = 10;
do {
    System.out.println("Number: " + num);
    num++;
} while (num < 5);
// Prints "Number: 10" once, even though 10 < 5 is false

The For-Each Loop

A simplified way to iterate over arrays and collections without managing an index manually.

int[] scores = {85, 90, 78, 92};
for (int score : scores) {
    System.out.println(score);
}

Break and Continue

for (int i = 1; i <= 10; i++) {
    if (i == 5) break;       // stops entirely at i = 5
    if (i % 2 == 0) continue; // skips even numbers
    System.out.println(i);   // prints 1, 3
}

Interview tip: A do-while loop always executes its body at least once — a classic trick question is asking what a do-while prints when its condition starts out false.